Spectroscopic imaging probes, devices, and methods

ABSTRACT

In part, the invention relates to a single clad fiber to multi-clad optical fiber connector for use in applying excitation light to a sample and obtaining reflected light from the sample. The connector can include a dual clad optical fiber portion and a single clad optical fiber portion in optical communication with the dual clad optical fiber portion. In one embodiment, a core of the dual clad optical fiber portion and a core of the single clad optical fiber portion have substantially similar indices of refraction. In one embodiment, excitation light is propagated by the core of the dual clad optical fiber. Further, in one embodiment, light reflected by the sample is propagated by the first cladding layer of the dual clad optical fiber portion.

FIELD OF INVENTION

This invention pertains generally to imaging probes and morespecifically to probes having color spectroscopic imaging andtomographic capabilities suitable for use in various applications suchas medical imaging, fiber-optic sensing, and industrial inspection.

BACKGROUND

Fiber optic sensing has been used for probing remote areas that havelimited spatial clearance. It is particularly useful in biomedicalresearch for probing internal cavities (e.g., body lumens) and inindustrial applications for monitoring hard-to-reach areas such as theinside of a small curved tube. One particular area of fiber opticsensing relates to imaging. A fiber bundle can be used to transmitimages coherently along the bundle. This approach is used in endoscopicapplications. However, fiber bundles often have a relatively large size,can be stiff and are generally expensive.

Another possible arrangement is to reconstruct an image by scanning asingle fiber over a sample of interest. Single-fiber imaging isparticularly attractive for certain applications, such as intravascularscanning, because of the small outer diameter of the single fiber.Single-mode fibers are used in applications that require coherenttransmission of light, such as low coherence interferometry and opticalcoherence tomography (OCT). In contrast, multimode fibers are used inapplications that do not require coherent transmission of light, butneed high collection efficiency, such as fluorescence imaging or Ramanspectroscopy.

One technical difficulty of performing single-fiber imaging is theseparation of the excitation light and the collection light. Because theexcitation light usually is much more intense than collected light, thecollected signals are harder to detect relative to the excitation lightreflected from various optical interfaces. As a result, it is difficultto obtain real-time color images of the vessel wall in the visible lightrange using existing optical coherence tomography (OCT) systems. OCTalso typically cannot measure light produced by incoherent opticprocesses such as fluorescence.

A need therefore exists for imaging methods and probes that can providereal-time color images that are suitable for use with an OCT system. Thepresent invention addresses this need and others.

SUMMARY OF THE INVENTION

The invention provides, in part, an apparatus for obtaining color andspectroscopic information using an imaging probe having a fixed orrotatable fiber. More specifically, devices, systems, and methods areprovided for obtaining OCT and/or color images from a sample by using anoptical fiber. The system can be used for obtaining OCT datasimultaneously along with other optical data such as fluorescence,Raman, and two-photon signals.

One embodiment of the present invention provides methods for obtainingcolor reflectance signals through a probe that includes one or moreoptical fibers. Suitable optical fibers include single-core fibershaving a single cladding layer (i.e., a single clad fiber (SCF)) ormultiple cladding layers (MCF) such as a dual clad fiber (DCF) which hastwo cladding layers.

In some embodiments, light composed of multiple wavelengths is launched(or injected) from a light source directly or indirectly (e.g., viaanother fiber) into the core of a dual clad fiber (DCF) fiber that isoptically connected to a probe. Injected light travels down the fibertowards the probe until the injected light exits the probe and impingeson the sample. Light reflected by the sample is then collected by theprobe and is transmitted back through the fiber towards the light sourcethrough the inner cladding of the DCF. Light passing back through thefiber is directed to one or more detectors that receive an opticalsignal or an electrical signal correlated to the optical signal. Thecollected signals are processed to subsequently form a colored orhyperspectral image of the sample. The signal detection or collectionsteps can be performed sequentially with one detector or in parallelwith multiple detectors.

Another embodiment of the present invention combines color reflectanceimaging with OCT. OCT is used to obtain the distances of the reflectionsfrom the sample to the probe. From these distances, such as penetrationdistances into a lumen, a 3D surface can be rendered. The color orhyperspectral reflectance images are then overlaid onto the 3D surfaceto reconstruct a 3D color surface or a 3D hyperspectral image.

Some embodiments of the invention provide methods to construct and usethe fiber-based devices that combine spectral data and OCT to generate acolor image of a body object such as an eye, tissue sample, or a lumensuch as a blood vessel.

Other embodiments of the present invention provide techniques thatcouple light into and out of a cladding layer of a DCF (ormultiple-clad, multiple-core fiber). In some embodiments, the techniquesinvolve first connecting a matching single-core fiber (SCF) that doesnot have a second outer clad layer to the DCF. The matching SCF hassimilar geometry, core composition, and cladding layers as the multipleclad fiber except that the matching SCF lacks the outermost claddinglayer of the DCF. Next the combined matched fiber is surrounded withindex-matching material and the applicable optical apparatus either toinject or collect light.

In one aspect, the invention relates to an optical system that includesa single clad to multi-clad optical fiber connector comprising a dualclad optical fiber portion and a single clad optical fiber portion. Inone embodiment, the dual clad optical fiber portion includes a firstcore portion, a first cladding layer adjacent the first core portion,and a second cladding layer adjacent the first cladding layer. The firstcladding layer and the second cladding layer have lower refractiveindices than the first core portion. The single clad optical fiberportion is in optical communication with the dual clad optical fiberportion. The single clad optical fiber portion includes a second coreportion and a first cladding layer adjacent the second core portion. Thesecond core portion and the first core portion have substantiallysimilar indices of refraction and together form a core. The first coreportion of the dual clad optical fiber is configured to propagateexcitation light to a sample. The first cladding layer of the dual cladoptical fiber portion is configured to collect light scattered from thesample. In another embodiment, the single clad optical fiber portioncomprises an outer surface and has a longitudinal axis. The outersurface defines an emission region wherein light propagating in thefirst cladding layer exits the emission region at an angle relative tothe longitudinal axis.

In another embodiment, the optical system further includes a lightsource in optical communication with the single clad optical fiberportion; a probe in optical communication with the dual clad opticalfiber portion; and a detector in optical communication with the singleclad to multi-clad optical fiber connector. The detector detects lightreflected by the sample and ejected by the first cladding layer of thedual clad optical fiber portion. In yet another embodiment, the opticalsystem further includes an OCT subsystem; and a beam splitter/combiner,the beam splitter/combiner in the optical path between the light sourceand the probe and in the optical path between the OCT subsystem and theprobe. Light from the OCT subsystem and light from the light source arecombined prior to being transmitted to the probe. In still yet anotherembodiment, the optical system further includes an optical coupler forcoupling light from the light source into the second core portion of thesingle clad optical fiber portion. In another embodiment, the opticalsystem further includes a rotatable optical coupler in the optical pathbetween the optical coupler for coupling light from the light sourceinto the second core portion of the single clad optical fiber portionand the probe. In still yet another embodiment of the optical system,the rotatable optical coupler in the optical path between the opticalcoupler for coupling light from the light source into the second core ofthe single clad optical fiber portion and the probe is positionedadjacent the optical coupler.

In one embodiment, the rotatable optical coupler is in the optical pathbetween the optical coupler for coupling light from the light sourceinto the second core portion of the single clad optical fiber portionand the probe is positioned within the optical path defined by thesingle clad fiber. In another embodiment, the rotatable optical couplerin the optical path between the optical coupler for coupling light fromthe light source into the second core portion of the single clad opticalfiber portion and the probe is positioned within the optical pathdefined by the double clad fiber. In still yet another embodiment, therotatable optical coupler in the optical path between the opticalcoupler for coupling light from the light source into the second coreportion of the single clad optical fiber portion and the probe is a partof the single clad to multi-clad optical fiber connector. In anotherembodiment, the optical system further includes an optical coherencetomography probe having a reflector configured for directing light fromthe core to the sample and receiving light from the sample into thefirst cladding layer.

In one embodiment, the system further includes a rotatable opticalcoupler in the optical path between the light source and the probe andwherein the probe rotates. In another embodiment, the optical systemfurther includes an optical coherence tomography subsystem configured toreceive (i) light or (ii) a signal derived from light returning alongthe core from the sample.

In another aspect, the invention relates to a method of collectingoptical coherence data and spectroscopic data from a sample. In oneembodiment, the method includes the steps of transmitting light in afirst material having a first index of refraction to the sample;receiving the light from the sample; transmitting scattered light fromthe sample having a first mode in the first material having a firstindex of refraction to a first detector, transmitting scattered lightfrom the sample having a second mode in a second material having asecond index of refraction to a second detector; and generating anoptical coherence tomography image of the sample having spectroscopicdata overlaid thereon. In another embodiment of the method, thescattered light having a first mode and the scattered light having asecond mode are transmitted coaxially in a fiber core and a firstcladding layer, respectively. In yet another embodiment of the method,the step of transmitting light in a first material having a first indexof refraction to the sample further comprises the step of rotating thefirst material.

In one embodiment of the method, the scattered light having a secondmode is transmitted in a first cladding layer. In another embodiment,the method further includes the step of terminating a second claddinglayer such that the scattered light having a second mode exits the firstcladding layer at an angle before reaching the second detector. Inanother embodiment, the optical coherence tomography image is a 3-Dimage and the spectroscopy data is a color representation of the sample.In yet another embodiment, the method further includes the step ofcalibrating for collection efficiency such that the optical coherencetomography image is in focus.

In yet another aspect, the invention relates to a method of collectingoptical coherence data and spectroscopic data from a sample. In oneembodiment, the method includes the steps of transmitting opticalcoherence tomography light through an optical fiber to the sample;receiving the optical coherence tomography light from the sample;transmitting scattered optical coherence tomography light from thesample to a first detector; transmitting a first spectroscopic lighthaving a first wavelength through an optical fiber to the sample;receiving the first spectroscopic light from the sample; transmittingthe first spectroscopic light from the sample to a second detector,transmitting a second spectroscopic light having a second wavelengththrough an optical fiber to the sample; receiving the secondspectroscopic light from the sample; transmitting the secondspectroscopic light from the sample to the second detector, registeringdata received from the optical coherence tomography light with datareceived from the first and second spectroscopic lights; and generatingan optical coherence tomography image of the sample having spectroscopicdata overlaid thereon.

In one embodiment, the invention relates to a single clad fiber tomulti-clad optical fiber connector for use in applying excitation lightto a sample and obtaining reflected light from the sample. The singleclad to multi-clad optical fiber connector includes a dual clad opticalfiber portion, the dual clad optical fiber portion comprising a core, afirst cladding layer adjacent the core, and a second cladding layeradjacent the first cladding layer, the first cladding layer and thesecond cladding layer having lower refractive indices than the core; anda single clad optical fiber portion in optical communication with thedual clad optical fiber portion, the single clad optical fiber portioncomprising a core and a first cladding layer adjacent the core. The coreof the dual clad optical fiber portion and the core of the single cladoptical fiber portion have substantially similar indices of refraction.The excitation light is propagated by core of the dual clad opticalfiber, and light reflected by the sample is propagated by the firstcladding layer of the dual clad optical fiber portion.

In one embodiment, the invention relates to a method for providingexcitation light to a sample and separating received reflected lightfrom the sample and includes the steps of: providing a single clad tomulti-clad optical fiber connector that includes a dual clad opticalfiber portion, the dual clad optical fiber portion comprising a core, afirst cladding layer adjacent the core, and a second cladding layeradjacent the first cladding layer, the first cladding layer and thesecond cladding layer having lower refractive indices than the core; anda single clad optical fiber portion in optical communication with thedual clad optical fiber portion, the single clad optical fiber portioncomprising a core and a first cladding layer adjacent the core, whereinthe core of the dual clad optical fiber portion and the core of thesingle clad optical fiber portion have substantially similar indices ofrefraction, and applying excitation light to the core of the dual cladoptical fiber, and extracting light reflected by the sample andpropagated by the first cladding layer of the dual clad optical fiberportion.

In one embodiment, the invention relates to an optical system thatincludes a single clad to multi-clad optical fiber connector thatincludes a dual clad optical fiber portion, the dual clad optical fiberportion comprising a core, a first cladding layer adjacent the core, anda second cladding layer adjacent the first cladding layer, the firstcladding layer and the second cladding layer having lower refractiveindices than the core; and a single clad optical fiber portion inoptical communication with the dual clad optical fiber portion, thesingle clad optical fiber portion comprising a core and a first claddinglayer adjacent the core, the single clad optical fiber portion foroptical communication with a light source; wherein the core of the dualclad optical fiber portion and the core of the single clad optical fiberportion have substantially similar indices of refraction; and a probe inoptical communication with the dual clad optical fiber portion, whereinexcitation light is propagated by core of the dual clad optical fiber,and wherein light reflected by the sample is propagated by the firstcladding layer of the dual clad optical fiber portion.

Another aspect of the invention is a method for providing excitationlight to a probe and separating received reflected light from the probe.In one embodiment, the method includes the steps of providing a singleclad to multi-clad optical fiber connector including a dual clad opticalfiber portion, the dual clad optical fiber portion comprising a core, afirst cladding layer adjacent the core, and a second cladding layeradjacent the first cladding layer, the first cladding layer and thesecond cladding layer having lower refractive indices than the core; anda single clad optical fiber portion in optical communication with thedual clad optical fiber portion, the single clad optical fiber portioncomprising a core and a first cladding layer adjacent the core. The coreof the dual clad optical fiber portion and the core of the single cladoptical fiber portion have substantially similar indices of refraction,and applying excitation light to the core of the dual clad opticalfiber, and extracting light received from the probe and propagated bythe first cladding layer of the dual clad optical fiber portion.

In another aspect, the invention relates to an optical system includingan optical light source; a single clad to multi-clad optical fiberconnector comprising: a dual clad optical fiber portion, the dual cladoptical fiber portion comprising a core, a first cladding layer adjacentthe core, and a second cladding layer adjacent the first cladding layer,the first cladding layer and the second cladding layer having lowerrefractive indices than the core; and a single clad optical fiberportion in optical communication with the dual clad optical fiberportion, the single clad optical fiber portion comprising a core and afirst cladding layer adjacent the core, the single clad optical fiberportion for optical communication with the optical light source; whereinthe core of the dual clad optical fiber portion and the core of thesingle clad optical fiber portion have substantially similar indices ofrefraction; and a probe in optical communication with the dual cladoptical fiber portion, wherein excitation light is propagated by core ofthe dual clad optical fiber, and wherein light reflected by the sampleis propagated by the first cladding layer of the dual clad optical fiberportion; and a detector in optical communication with the single clad tomulti-clad optical fiber connector, wherein the detector detects lightreflected by the sample and ejected by the first cladding layer of thedual clad optical fiber portion.

In another embodiment, the optical system includes an optical couplerfor coupling light from the optical light source into the core of thesingle clad optical fiber portion. In another embodiment, the opticalsystem includes a rotatable optical coupler in the optical path betweenthe optical coupler for coupling light from the optical light sourceinto the core of the single clad optical fiber portion and the probe. Inone embodiment, the rotatable optical coupler in the optical pathbetween the optical coupler for coupling light from the optical lightsource into the core of the single clad optical fiber portion and theprobe is positioned adjacent the optical coupler. In one embodiment, therotatable optical coupler in the optical path between the opticalcoupler for coupling light from the optical light source into the coreof the single clad optical fiber portion and the probe is positionedwithin the optical path defined by the single clad fiber. In oneembodiment, the rotatable optical coupler in the optical path betweenthe optical coupler for coupling light from the optical light sourceinto the core of the single clad optical fiber portion and the probe ispositioned within the optical path defined by the double clad fiber. Inone embodiment, the rotatable optical coupler in the optical pathbetween the optical coupler for coupling light from the optical lightsource into the core of the single clad optical fiber portion and theprobe is a part of the single clad to multi-clad optical fiberconnector.

In one aspect, the invention relates to a method for obtaininginformation about a sample that includes providing a single clad tomulti-clad optical fiber connector comprising a dual clad optical fiberportion, the dual clad optical fiber portion comprising a core, a firstcladding layer adjacent the core, and a second cladding layer adjacentthe first cladding layer, the first cladding layer and the secondcladding layer having lower refractive indices than the core: and asingle clad optical fiber portion in optical communication with the dualclad optical fiber portion, the single clad optical fiber portioncomprising a core and a first cladding layer adjacent the core, whereinthe core of the dual clad optical fiber portion and the core of thesingle clad optical fiber portion have substantially similar indices ofrefraction; and providing a probe in optical communication with the dualclad optical fiber portion and in optical communication with the sample,applying excitation light to the single clad optical fiber portion;wherein excitation light is propagated by core of the dual clad opticalfiber, and wherein light reflected by the sample is propagated by thefirst cladding layer of the dual clad optical fiber portion; anddetecting light reflected by the sample and ejected by the firstcladding layer of the dual clad optical fiber portion. In oneembodiment, the method includes the step of rotating the probe. Inanother embodiment, the method further includes the step of rotating thesingle clad to multi-clad optical fiber connector.

In one aspect, the invention relates to an optical imaging system. Inone embodiment, the system includes an optical light source; a singleclad to multi-clad optical fiber connector comprising a dual cladoptical fiber portion, the dual clad optical fiber portion comprising acore, a first cladding layer adjacent the core, and a second claddinglayer adjacent the first cladding layer, the first cladding layer andthe second cladding layer having lower refractive indices than the core;and a single clad optical fiber portion in optical communication withthe dual clad optical fiber portion, the single clad optical fiberportion comprising a core and a first cladding layer adjacent the core,the single clad optical fiber portion for optical communication with theoptical light source; wherein the core of the dual clad optical fiberportion and the core of the single clad optical fiber portion havesubstantially similar indices of refraction; and a probe in opticalcommunication with the dual clad optical fiber portion, whereinexcitation light is propagated by core of the dual clad optical fiber,and wherein light reflected by the sample is propagated by the firstcladding layer of the dual clad optical fiber portion; a detector inoptical communication with the single clad to multi-clad optical fiberconnector, wherein the detector detects light reflected by the sampleand ejected by the first cladding layer of the dual clad optical fiberportion; an OCT module; and a beam splitter/combiner, the beamsplitter/combiner in the optical path between the light source and theprobe and in the optical path between the OCT module and the probe;wherein light from the OCT module and light from the light source arecombined prior to being transmitted to the probe. In another embodimentthe system further includes a rotatable optical coupler in the opticalpath between the optical light source and the probe and wherein theprobe rotates.

In another aspect, the invention relates to a method for generating anoptical image. In one embodiment the method includes providing a probein optical communication with the dual clad optical fiber portion and inoptical communication with the sample, applying excitation light to thesingle clad optical fiber portion; wherein excitation light ispropagated by core of the dual clad optical fiber, and wherein lightreflected by the sample is propagated by the first cladding layer of thedual clad optical fiber portion; providing an OCT module in opticalcommunication with the probe; providing a beam splitter/combiner, thebeam splitter/combiner in the optical path between the light source andthe probe and in the optical path between the OCT module and the probe;combining light from the OCT module and light from the light sourceprior to being transmitted to the probe and detecting light reflected bythe sample and ejected by the first cladding layer of the dual cladoptical fiber portion. In another embodiment, the method furtherincludes the step of rotating the probe. In still another embodiment,the method further includes the step of constructing an OCT image fromthe light reflected by the sample. In yet another embodiment, the methodfurther includes the step of analyzing light reflected by the sample andejected by the first cladding layer and overlaying the analyzed light onthe OCT image. In one embodiment of the method, the OCT image is a 3-Dimage and the analyzed light is a color overlay on the 3-D image.

The devices, systems and methods are explained through the followingdescription, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawings will be provided by the Office upon request and paymentof the necessary fee.

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.The drawings associated with the disclosure are addressed on anindividual basis within the disclosure as they are introduced.

FIG. 1A is a schematic diagram of an illustrative embodiment of acoupler suitable for imaging with a single-fiber probe constructed inaccordance with the invention.

FIG. 1B is a schematic diagram showing a cross section of anillustrative embodiment of a single clad fiber in accordance with theinvention.

FIG. 1C is a schematic diagram showing a cross section of anillustrative embodiment of a multiple clad fiber in accordance with theinvention.

FIG. 2 is a schematic diagram of a cladding coupler constructed inaccordance with an illustrative embodiment of the invention.

FIG. 3A is a block diagram of an imaging system constructed inaccordance with an illustrative embodiment of the invention.

FIG. 3B is a schematic diagram of an imaging system in accordance withan illustrative embodiment of the invention.

FIGS. 4A-D are schematic diagrams of exemplary optical arrangements forguiding light from a fiber to another light guide or to a detectorconstructed in accordance with illustrative embodiments of theinvention.

FIG. 5 is a graph showing measurement of collection efficiency as afunction of sample distance to the probe of a light source through anembodiment of the system constructed in accordance with the invention.

FIG. 6 shows an exemplary color image of a color wheel pattern printedon a white paper, obtained by a system and probe built in accordancewith an illustrative embodiment of the invention.

FIGS. 7 A-D are schematic diagrams of different embodiments of arotatable device for obtaining images from a rotating probe inaccordance with an illustrative embodiment of the invention.

FIG. 8 is a schematic diagram of an embodiment of a device for combiningtwo wavelength bands to improve throughput in accordance with anillustrative embodiment of the invention.

FIG. 9 is a schematic diagram showing an embodiment of a device thatacts both as a rotary joint and as a DCF coupler constructed inaccordance with an illustrative embodiment of the invention.

FIG. 10 shows an example of an image obtained using a rotating imagingprobe having an optical fiber in accordance with an illustrativeembodiment of the invention.

FIG. 11A is a schematic diagram of an embodiment of a system forcombining spectroscopic data, such as color information, and OCT imagingdata, such as distance measurements, constructed in accordance with theinvention.

FIG. 11B is an exemplary method of generating a combined tomographic andspectroscopic dataset or image in accordance with an illustrativeembodiment of the invention.

FIG. 12 shows an example of an OCT image generated using an imagingprobe embodiment of the invention.

FIG. 13 shows a spectroscopic measurement superimposed on a 2D OCTimage, constructed in accordance with an illustrative embodiment of theinvention.

FIG. 14A shows a spectroscopic measurement superimposed on a 3D OCTimage, constructed in accordance with an illustrative embodiment of theinvention.

FIG. 14B shows a spectroscopic measurement superimposed on a 3D OCTimage that resembles the view from a conventional forward-viewingendoscope constructed in accordance with an illustrative embodiment ofthe invention.

FIG. 15 shows a calibrated spectroscopic image constructed in accordancewith an illustrative embodiment of the invention.

FIG. 16 is a schematic diagram of a catheter delivered imaging probeconfigured for spectroscopic imaging in accordance with an illustrativeembodiment of the invention.

FIG. 17A is a schematic diagram of a forward scanning probe tip showinglight propagation and scattering relative to a core and cladding inaccordance with an illustrative embodiment of the invention.

FIG. 17B is a schematic diagram of a side scanning probe tip showinglight propagation and scattering relative to a core and cladding inaccordance with an illustrative embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1A shows an exemplary optical coupler 10, constructed in accordancewith an illustrative embodiment of the invention. A single-clad fiber(SCF) 12 is optically coupled to a dual-clad fiber (DCF) 16. In someembodiments, excitation light injected into the core 18 of SCF 12,enters the core 20 of DCF 16, and then propagates to a rotating imagingprobe at the other end of the DCF 16 (not shown). FIG. 1B shows across-sectional view of the SCF 12 of FIG. 1A. SCF 12 has a core 18 anda single cladding layer 22. FIG. 1C shows a cross-sectional view of theDCF 16 of FIG. 1A. DCF has a core 20, a first (or inner) cladding layer24, a second (or outer) cladding layer 26 and a jacket 27. Typically,the diameter of the outer cladding 26 matches the diameter of thecladding 22 in the SCF because most fibers are the same size. However,variations in fiber sizes and custom fibers are possible such that thediameters of coupled fibers or cladding layers can differ.

FIG. 2 shows further details of an embodiment of a DCF coupler 10constructed in accordance with an illustrative embodiment of theinvention. The coupler 10 is used to facilitate imaging a sample (leftside, not shown) and detecting the return light at a detector (rightside, not shown). In this embodiment, a DCF fiber 16 is connected to amatching SCF 12 that does not have a second, outer cladding layer 27.The SCF 12 otherwise has similar geometry, core composition, andcladding as the DCF 16. In one embodiment one end of the matched SCF 12is surrounded by index-matching material and is coupled to an applicableoptical apparatus to inject or collect light, while the other end of thematched SCF 12 is optically connected at interface 14 to the DCF 16. Theconnection 14 between the DCF 16 and the matching SCF 12 can be achievedby, for example, fusion splicing or by butt-coupling.

With continued reference to FIG. 2, the DCF 16 has a core 20, an innercladding layer 24 and an outer cladding layer 26. The goal of theconfiguration is to couple light into and out of the inner cladding 24of the DCF. The core 18 of the SCF 12 is matched to the core 20 of theDCF 16 in both diameter and refractive index, and the SCF cladding 22 ismatched to the inner cladding 24 of the DCF 16 in refractive index.

Considering the example of coupling light out of the inner cladding ofthe DCF; excitation light is injected from a light source (notshown—right side of the figure) into core 18 of SCF 12 and enters core20 of DCF 16 via coupling interface 14. Excitation light then propagatesdown core 20 to a probe at the end of DCF 16 where the excitation lightexits the probe and impinges on a sample. Subsequently, light (λ)reflected by the sample is collected by the probe and is guided in theinner cladding 24 of DCF 16 because the outer cladding 26 layer haslower refractive index than the inner cladding layer 24. Some reflectedlight also enters the core 20 of DCF 16. At the interface 14 between theDCF fiber 16 and the SCF 12, because the refractive indices are wellmatched, both the light in the core 20 and in the inner cladding 24 ofthe DCF propagate into the core 18 and the cladding 22 of the SCFwithout significant interface reflection and intensity loss.

Reflected light in the inner cladding 24 of DCF 16 is guided into thecladding 22 of the SCF 12. Because the SCF 12 does not have an outercladding layer, light can be readily guided out of the cladding 22 bysurrounding the SCF 12 with a higher index media such that the light isno longer guided along the fiber. The shape of such light propagation isa cone structure 31 whose angle α is determined by the relativerefractive indices of the cladding layer and the media. One of theregions from which the light cone exits the outer surface of the fiberis an emission region. A detector can be placed near such as region tocollect a spectroscopic signal. To the extent a jacket or other coatingis applied to a portion of the outer surface of the fiber segment wherethe cone would otherwise form, the region for coupling light out of thefiber, such as the emission region, can be specified and controlled. Thelight cone escaping from the SFC 12 can be captured by a detectordirectly in its path or redirected by optical apparatus. The sameprinciple can be extended to arbitrary cladding geometries.

FIG. 3A is a block diagram showing the basic components of an imagingsystem constructed in accordance with an embodiment of the invention.The imaging system includes a light source 30, a fiber coupler 32 (e.g.,a mirror, lens, or prism assembly), a DCF coupler 34, a sample imagingprobe 36, an optical receiver 38, and electronics 40 for generatingcontrol signal and data recording. The system can include a single-corefiber (e.g., a SCF) which carries injected light from the light source30 to the DCF coupler 34. The probe 36 can be forward scanning, sidescanning or other suitable configurations.

Referring to FIG. 3B, in one embodiment a light source 30 is coupled tothe core of a single-core fiber (e.g., a SCF) 12 by a fiber coupler 32.This excitation light from the source 30 is injected through a fibercoupler 32 and into the core 18 (FIG. 1) of the single-core fiber 12,passes through DCF coupler 34, and continues propagating in the innercore 20 of DCF 16 until it exits the fiber through the probe 36 andpropagates to the sample. Some light is reflected by the sample and thisreflected light is collected by the probe 36 and transmitted to both theinner cladding 24 and the core 20 of the DCF (FIG. 1). Because thediameter and the numerical aperture of the inner cladding 24 are largerthan those of the core 20, more light is collected by the inner cladding24 than by the core 20. The light that is collected by the innercladding 24 propagates along the inner cladding 24 of the DCF 16 back tothe DCF coupler 34, where the light is coupled out of the fiber toanother fiber or directly to an optical receiver 38, such as an opticaldetector or a spectrometer. The optical receiver can includephotodiode-based detectors or other components suitable for convertingan optical signal to an electric signal.

In one embodiment, a single detector can be used in the optical receiver38 to collect light propagating along or within the light fielddesignated by cone 31 in FIG. 2 or as otherwise shown by the coupler 34.The optical receiver 38 can be used to capture serially generatedsignals associated with different colors or wavelengths of light.Alternatively, a demultiplexer or other device can be used to collect aplurality of wavelengths or colors in parallel and direct thedemultiplexed beams to multiple detectors at the optical receiver 38such that each detector is used to capture each of the plurality ofwavelengths or colors propagated through cladding 22. However,sequential processing of signals containing color information on onedetector is preferred as a result of the cost savings and reducedcomplexity associated with not having to deal with parallel signals andthe demultiplexing of the same.

As shown in FIG. 3B, electronic circuits 40 are used to control andsupply power to the light source, the optical receiver, etc. Additionalelectronics and computers can be added to for further control signals,coordinating probe movement, data processing and displaying. Ademultiplexer and a detector array used in receiver 38 can also be inelectronic communication with suitable control and power circuits 40.

In one embodiment, the light source can include, without limitation, abroadband light source such as superluminescent white light sources,supercontinuum generation light sources, black-body radiation lightsources, light emitting diodes (LED), laser-pumped phosphors,superluminescent light emitting diodes (SLED), or broadband lasers suchas Ti:Al₂O₃ lasers.

In one embodiment, light from a given source is coupled into thesingle-core fiber and propagates there through with a level of intensitysuitable for propagating to and from a sample such that a compositeimage can be generated. For this, high-irradiance light sources withsuitable emission angles, such as the lasers or SLEDs, are preferredover the other sources such as blackbody radiation, LEDs, or phosphorlight sources. In another embodiment, the light sources may beconstructed of an assembly of light sources of different wavelengths.Although the individual light sources may be either broad or narrowband, the assembly is designed to cover a spectral band of interest. Forexample, a white light source can be made by combining three narrowbandlasers that emit red, green and blue light. The light of differentwavelengths can be combined by dichroic mirrors or by prisms. To achievethe desired imaging results, the light sources are selected andconfigured to provide a suitable contrast level for each application. Inaddition, it may be desirable to use multiple light sourcessimultaneously, depending on the imaging application.

In one embodiment, the light sources are chosen to generate images thatresemble the images seen by human eye in a relatively natural setting.To achieve this, broadband white light sources with spectrum coveragewithin the visible light spectra (380-750 nm) are chosen. Examples ofsuch light sources include white superluminescent sources,supercontinuum generation sources, blackbody radiation sources, whiteLEDs, and fluorescence light sources. In addition, because human eyeshave three types of color-sensing retinal cells, each responding to red,green, and blue colors, an assembly of narrowband light sources can becombined to achieve the same effect. For example, three lasers withindividual outputs that span most of the visible spectrum (e.g., laser 1in the 580-750 nm band, laser 2 in the 495-580 nm band and laser 3 inthe 380-495 nm band), can be combined by dichroic mirrors to generatewhite light.

In another embodiment, the light sources are chosen to generate atailored level of contrast for a particular disease signature,structural feature, or chemical compositions. For example, becausehemoglobin in the red blood cell has a sharp transition of opticalabsorption around 580-620 nm, a light source or an assembly of lightsources that spans this range offers high sensitivity for thrombusdetection in blood vessel imaging. In another example, because thecholesterol and cholesterol esters have an absorption signature in theinfrared spectrum around 1680-1720 nm, light sources spanning that rangeoffer high sensitivity for the detection of lipid plaques during bloodvessel imaging.

In another embodiment, a DCF coupler includes a device configured tomaintain the continuity of the light propagation from the core of thesingle-core fiber to the core of the DCF, while allowing the light atthe inner cladding of DCF to be coupled out. An optical apparatus can beincorporated to aid in collection of reflected light or ejection ofexcitation light in the DCF coupler 34. FIG. 4A shows an embodiment ofsuch an optical apparatus 80.

As shown, a mirror 82 with a central hole 82 a allows the fiber 12 topass through but reflects most of light (λ) escaping the cladding offiber 16 in a direction substantially perpendicular to the fiber 16. Thelight escaping the fiber has a conical profile as previously discussedwith respect to FIG. 2. In one embodiment, a lens assembly 86 is used tofocus the light to a small aperture for collection or measurement. Ifthe refractive index matching media 88 surrounding the fibers 12 and 16is a liquid, the fibers 12 and 16 can be either stationary or rotating.If the fibers are rotating, as long as the mirror 82 does not rotate,the light λ is guided to a stationary point 87.

FIG. 4B shows a similar embodiment except the mirror 82′ is moved out ofthe matching refractive index matching media 88 for ease ofmanufacturing. FIG. 4B also permits fiber rotation even if the media issolid or is confined inside a solid rotating container. In theembodiments of both FIGS. 4A and 4B, the flat mirror 82 can be replacedwith a curved mirror (not shown) to aid in light focusing andcollection. FIG. 4C shows another embodiment in which the surroundingrefractive index matching media 88 is shaped such that the light isreflected and focused by the shaped reflecting surface 90.

FIG. 4D shows another embodiment in which a lens assembly 86′ has a hole86 a that allows the fiber 12 to pass through but the out-coupled light(λ) is redirected by the lens assembly. The optic elements andassemblies mentioned herein can also be embedded in or molded in placewith the surrounding refractive index matching media rather than beingstand-alone. To improve optical and mechanical properties of the device,anti-reflective coatings and other performance-enhancing coating may beapplied to interfaces. It should be noted that FIGS. 4A-D only showexamples of optical arrangement. Other configurations are possiblewithout departing from the scope and spirit of the invention.

The distal part of the miniature probe provides optics for bothlaunching light into the sample and collecting reflected light from thesample. It typically includes a refractive lens or a GRIN lens and maycontain a scanning mechanism. Other configurations are also possible,such as those based on shaped reflectors or shaped lens. Because thecore of a DCF has smaller diameter and often has a smaller numericalaperture than the inner cladding, back reflected light from the core iscollected by the inner cladding, resulting in potential cross-talk.Therefore, the optical path is configured to minimize back reflection.

When the incident light interacts with the sample, it can undergovarious optical processes that include absorption, scattering,reflection, fluorescence, and non-linear interactions. Once scatteredfrom the sample, such as an artery, a portion of modified lightpropagates back and is collected by the aperture of the probe. Thecollection efficiency associated with this portion of light is a complexfunction of the numerical aperture (NA) of the DCF core, the NA of theDCF inner cladding, and the properties of the lens. FIG. 5 shows thecollection efficiency of 532 nm light delivered and collected by animaging probe and associated data processing system that includes awhite diffuse reflection standard.

When the light collected from the sample propagates back along the innercladding and reaches the DCF coupler, the light is coupled out (i.e.,out-coupled) of the cladding. In one embodiment, out-coupled light isfirst separated by prism or gratings, or by a set of dichroic orabsorption filters (not shown). After the separation, the intensities oflight of different wavelengths are measured by optical detectors. Thisdemultiplexing process is used when non-OCT light, i.e., the light usedfor color information, is delivered to a sample simultaneously such thatmultiple colors of light arrive in parallel. The measurement of eachdetector represents the intensity of the light in a particularwavelength range. In another embodiment, the out-coupled light ismeasured by a spectrometer. In yet another embodiment, the out-coupledlight is detected by one optical receiver, but the lights of differentwavelengths are encoded either by frequency-division multiplexing ortime-division multiplexing.

Alternatively, the out-coupled light can include one wavelength of lightthat is transmitted along the inner cladding while the probe isstationary, moving or otherwise rotating. Several different wavelengthsof light can be sent and received along the inner cladding to reach thesample and return for processing before the spin rate of the opticalfiber causes it to translate to a new spatial position of the sample.

In addition, the multiplexing arrangement can be enhanced if theexcitation light source is made of an assembly of light sources ofdifferent wavelengths. In frequency-division multiplexing, the lightsources of different wavelength are encoded with different modulationfrequencies. In time-division multiplexing, the light sources ofdifferent wavelengths are turned on at different time intervals andelectronic decoders are used to separate the signals from the differentwavelengths.

To obtain a visual image, either the probe head or the sample can betranslated in a raster motion to collect 2D or 3D information. Suchscanning mechanisms are similar to those widely used for otherapplications such as confocal microscopy or OCT. FIG. 6 shows an exampleimage of a color wheel pattern printed on a white paper, which wasobtained by raster-scanning the probe in FIG. 3A across the sample. Thecolors are resolved accurately and with high spatial resolution.

For some types of samples, such as blood vessels or thegastro-intestinal (GI) tract, the spiral scanning is preferred and moreefficient than raster scanning. In order to achieve this, an opticalrotational joint is used to connect the optical fiber to the lightsource. FIGS. 7A-7D show four respective embodiments of a rotary joint.These embodiments are suitable for implementing spiral scanningaccording to an embodiment invention. The rotary joint can be located atthe fiber coupler 32, at the single-core fiber 12, at the DCF coupler34, or at the DCF 16; each arrangement has advantages for specificapplications.

Considering FIG. 7A, when the rotary joint 100 a is located at the fibercoupler 32, the rotary joint 100 a transfers light from the sourcesdirectly to a single-core fiber 12 without intervening fiber optics.This arrangement simplifies the optical design of the rotary joint 100 aand mitigates cross talk because the cladding light in the single-corefiber is not guided. No excitation light propagates in the cladding.Instead, some light from sample is transmitted back in the cladding.Thus, the light in the core, or such scattered light configured for useby an OCT system, is collected once scattered from the system and lightreturning from the sample configured to generate color information forthe sample is collected in the cladding.

However, because the DCF coupler 34 rotates in this case, a specialdesign is required to ensure that the DCF coupler maintains couplingefficiency and mechanical integrity during rotation. If the light sourceis broadband, it is often difficult to design a single lens that focusesall the wavelengths efficiently into a single rotating fiber. Thus, itsometimes is advantageous to divide the light into several wavelengthbands using dichroic mirrors or prisms (not shown), and to add optics toadjust the optical focusing of different wavelength bands individually.This is especially useful if the light source is made of an assembly ofmultiple narrowband sources.

FIG. 8 shows an embodiment of such a device for two wavelength bands λa,λb from two different sources with lenses 33, 33′ combined by a dichroicmirror 83 prior to being refocused by lens 32 injected into the core ofSCF 12 through rotary joint 100 a.

Referring to FIG. 7B, when the rotary joint 100 a, b is located at thesingle-core fiber, the rotary joint 100 a, 100 b transfers light fromone single-core fiber 12 a to another single-core fiber 12 b. Becausethe single-core fibers are used widely, many off-the-shelf rotary jointscan be used for this purpose. Further, since the cladding light is notguided, cross-talk of core and cladding light is reduced across thejoint.

Referring to FIG. 7C, when the rotary joint 100 a, 100 b is located atthe DCF coupler 34, the rotary joint transfers the light from the coreof the single-core fiber 12 to the core of the DCF 16, and collects thelight from the inner cladding of DCF to another multi-mode fiber ordirectly to the optical receiver. This configuration reduces possibleoptical interfaces, saves space and increases the light couplingefficiency.

Referring momentarily to FIG. 9, an optical arrangement is shown thatcouples light from the cladding of a rotating DCF. The single-core fiber12 is on the left side and the DCF 16 is on the right side. This issimilar to what is shown for FIG. 4A, but a rotating fiber and with thelens 86 being located in a refractive index matching medium 88. Thefiber ends are cleaved and submerged in an index matching fluid 88 witha refractive index matched to the cladding of the single-core fiber 12.

In one embodiment, the two fibers are placed in close proximity suchthat the fiber ends 12 a, 16 a are within confocal distance of eachother. With this configuration, there is strong coupling between thecore of the single-core fiber 12 and the DCF 16 such that most opticalpower from the single-core fiber transmits to the core of the DCF.However, because the surrounding media 88 is refractive matched to thecladding of the single-core fiber, the light exiting from the innercladding of the DCF passes unguided and unobstructed into thesurrounding media. This light can be either be detected directly bydetectors or redirected by optics such as a mirror 82 and lens 86 towarda detector or another fiber.

Referring to the FIG. 7, FIG. 7D depicts an embodiment in which therotary joint 100 a, 100 b is located at the DCF 16, the rotary joint 100a, 100 b transfers light from the core and the inner cladding of onefiber portion DCF 16 a to the core and the inner cladding of the otherfiber portion DCF 16 b, respectively. In this case, the DCF coupler 34is stationary and, hence, easier to manufacture. However, the rotaryjoint 100 a, b is configured for use with a DCF fiber. In oneembodiment, the joint 100 a, 100 b is configured to prevent lighttraveling in the core from propagating in the cladding such thatunwanted cross-talk between the different light modes is prevented orreduced to an acceptable level.

Once rotation of the probe is achieved, the probe is translated alongthe axis to acquire a spiral scan. This process of pulling back theprobe along the axis allows OCT data to be collected over the length ofa sample. FIG. 10 shows an example of an image reconstructed from dataacquired from a spiral scan of a lumen acquired with an embodiment ofthe system. The sample lumen imaged in this example is rolled paper,printed with a repetitive rainbow color pattern. Because the collectionefficiency is dependent on the distance from the probe to the sample andthe probe is not exactly centered inside the sample, sample locationsthat are farther away from the probe appear darker.

Although the above methods provide color imaging, the distance from thesample to the probe cannot often be measured accurately. To achieveaccurate depth imaging, the present invention provides means forcombining color imaging and OCT imaging. Most of the optical componentsshown in FIGS. 7A-7D, including the core of the single-core fiber, thecore of the DCF, the rotary joint, the DCF coupler, and the probe can bemade to support the single-mode light propagation required by OCT.

FIG. 11A shows a schematic of an embodiment of a combined OCT andspectroscopic system. A beam splitter/combiner 108 is used to combinethe light from an OCT apparatus 44 and the light from a spectroscopiclight source 30. The beam splitter/combiner 108 can be of any type thatpasses a sufficient fraction of light from the two input paths,including but not limited to, dichroic mirrors, fiber beam combiners,and prisms. The light then travels along the core of a fiber 12 b,passing through a rotary joint 100 a, 100 b, a DCF coupler 34, a probe36 and is incident onto the sample. The collected light in the DCF 16has two parts, the light propagating along the core and that propagatingalong the inner cladding. At the DCF coupler 34, these two light beamsseparate into the two paths. A filter can be used on the exit light fromthe inner cladding to remove the OCT light (not shown). The lightcollected in the core from the sample can be compared with referencelight using an interferometer to generate depth measurements, as part ofthe OCT subsystem. Each depth measurement or a subset of the depthmeasurements can be matched with a spectroscopic signal to provide colorinformation relative to the measured position of the sample.

Alternatively, a wavelength-selective detector that it is not responsiveto the OCT light can be employed to detect the reflected spectroscopiclight. For the cases in which it is advantageous to use the OCT light asa wavelength component for the spectroscopic analysis, the receiver canbe made to receive both the OCT light and the spectroscopic light. Thelight propagating along the core travels across the DCF coupler 34, therotary joint 100 a, 100 b, and the beam splitter/combiner 108 to arriveback to the OCT subsystem 44. Because the spectroscopic component of thelight is incoherent with respect to the OCT light, it does not generatean OCT signal.

Under other circumstances, if the spectroscopic component of the lightgenerates background noise that degrades the signal to noise ratio ofthe OCT signal, a filter can be inserted into the optical path to thedetector to remove it. It should be noted that although the rotary joint100 a, 100 b is located between the beam splitter/combiner 108 and theDCF 34 coupler in FIG. 11A, all possible combinations and permutationsof arrangements of the joints and optical elements shown implementationsand are within the scope of the invention.

One embodiment of the system employing a white light source 30 for RGBimaging and an OCT subsystem 44 based on swept-source technology, suchas using a swept source laser as the source for the light injected intothe core and scattered from a sample, and a probe were constructedsimilar to the configuration shown in FIG. 11A. The OCT system used asingle-mode Corning SMF-28 fiber 12. The custom-made DCF 16 had a coreand inner cladding matched to the core and the cladding of the SMF-28fiber, except the inner cladding had a diameter about 100 μm instead of125 μm for the SMF-28 fiber. The outer cladding of the DCF had adiameter of about 125 μm. In the most distal end of the probe 36, a GRINlens was attached to achieve optical focusing.

In addition, the probe was rotated at 10 Hz while the pullback speed wasapproximately 1 mm/sec. For each rotation, approximately 450 axial linesor depth measurements at different points of rotation were collected forOCT and 67 pixels were collected for spectroscopy. Although this systemwas designed to measure the reflectance and scattering from the innersurface of a tubular structure, it could be readily modified to detectfluorescence, two-photon, Raman, and other optic processes using thesame principles. Hence, the test system constitutes an example, ratherthan the scope of this invention.

An exemplary embodiment of a method suitable for generating a combinedOCT/Spectroscopy image is illustrated in FIG. 11B. As shown, the OCT andspectroscopy signals are both obtained. The OCT images are generatedfrom the OCT signals from the fiber core using an interferometer-basedsubsystem such as OCT subsystem 44. The spectroscopy signal is firstdivided by the source spectral intensity to remove the source powervariation. The resulting spectroscopy signal is then assigned a colorusing color mapping to generate a spectroscopy image. The spectroscopyimage is overlaid on top of the OCT image to obtain the combined image.An exemplary color mapping is shown in FIG. 13 as described below.

FIG. 12 shows an example OCT image of a sample obtained through thesystem of FIG. 11A and the combined OCT and spectroscopy probe. Anexplanted stented coronary artery was used as the sample. In thisexample, the axial and the lateral resolutions of the OCT image arepreserved. The sample features, such as the artery wall structures(intima, media, advantitia), and the stent struts 110 are also preservedand are indistinguishable from images obtained by a stand-alone OCTapparatus.

Because the OCT light and the spectroscopy light share the same opticalpath in the probe, although coaxial in some embodiments, geometricalregistration of the OCT and spectroscopic images is easily accomplished.After OCT image is obtained, the spectroscopic images 130 can beoverlaid on top of OCT images 132 (FIG. 13). There are many ways bywhich the combination images can be displayed. FIG. 13 shows an examplemethod to overlay the spectroscopic information in a 2D OCTcross-sectional image. The OCT image is displayed similar to those inthe stand-alone OCT apparatus; the spectroscopic information can bedisplayed as numerical values, in full color, or in pseudo color, as acolor map, around the lumen wall, the circumference, or other contours.Each cross-section of the lumen has OCT measurements that provide depthinformation that can be paired with color information for each scanline. By combing these cross-sections or otherwise topographicallyprocessing the data, a 3D color image of a sample can be generated.

FIG. 14A shows the result of overlaying the spectroscopic information ona 3D OCT image. 3D reconstruction of the artery 140 is achieved usingthe 3D OCT dataset and the spectroscopy image is displayed on the lumenas colors of differing intensity. The color map can be a color surfaceas opposed to a color shape, such as the substantially circular colormap of FIG. 13 or any real or pseudo color representation. FIG. 14Bshows yet another method to overlay the spectroscopic information in a3D OCT that resembles the view typically achieved by a forward viewingendoscope. Once the OCT data has been captured through the fiber coreportion, it can be rendered and viewed from any angle and color based onthe spectroscopic signals obtained.

Because the optics often exhibit chromatic aberration, somepost-processing of the spectroscopic image is usually required toachieve accurate assessment. As shown previously in FIG. 10, the lightcollection efficiencies vary depending on the distance from the probeand the wavelengths. Because OCT is able to measure the distance fromthe probe to the sample accurately, it offers an opportunity to correctfor this aberration by calibrating the spectroscopic image according topre-recorded calibration curves. The image in FIG. 15, which is similarto the image in FIG. 10, shows a significant reduction in focusingartifacts after calibration for collection efficiency.

In vivo blood vessel imaging imposes a few additional requirements forcombined spectroscopic and OCT imaging according to the presentinvention. Because the blood is not transparent, the blood has to bedisplaced to obtain accurate imaging. The present invention enablessimulation and rapid acquisition of OCT and spectroscopic data as bloodis displaced by injecting a liquid flushing solution. For intravascularimaging, data is collected with a catheter with internal optics that canbe rotated rapidly and pulled back within a transparent outer sheath.FIG. 16 illustrates the major structures that lie in the optical path atthe imaging locus in a catheter that is compatible with bothspectroscopic and OCT imaging. The catheter 150 may include an imagingfiber 160, accessory optics such as lens and prisms, and one or morelayers of protective sheaths 162 (usually made of plastic or glassmaterials).

In one embodiment, the spaces between the walls of the sheaths andbetween the outermost sheath and the vessel wall 164 are filled withliquid. To reduce undesired back reflections as much as possible, it isimportant that the refractive index of materials in the optical path tobe matched as closely as possible. The suitable liquid for filling gapsinside the catheter includes, but is not limited to silicone oil,glycerol, and radio-opaque contrast solution. Because its refractiveindex closely matches the refractive indices of plastic sheath material,the angiographic contrast solution is the preferred liquid for flushingblood from the lumen 165.

FIG. 17A illustrates an imaging fiber 170 for an OCT imaging probeconfigured for spectroscopic signal collection. The imaging fiber orprobe tip 170 is disposed in a lumen 165 having walls 164. Light from anoptical source not shown is focused to a point or region 173. As shown,the fiber is configured for forward scanning such that it can imagelumen objects 174 or material disposed in the lumen 165 such as plaques174. A optical element 172, such as a lens, is in optical communicationwith the imaging fiber 170. The fiber 170 includes a core 20, a cladding24, and a jacket 27. In some embodiments, jacket 27 is absent.Typically, the fiber core 20 is in optical communication with the lightsource, an interferometer and one or more detectors such asphotodiode-based receivers or detectors.

As shown, by the light rays and arrows, light from the core 20, depictedas a dotted pair of lines, propagates from the core 20 and into thelumen 165 until reaching a focus 173 on lumen object 174. After thelight from the core 20 is scattered from the lumen object 174, it isreceived by the core 20 and cladding 24. The returning scattered lightis shown by the solid lines and arrows pointing to the cladding 24. Thescattered light collected in the core can be used for OCT imagegeneration. Similar, the scattered light entering the cladding can beused to generate a color map or color representation of the OCT datacollected. The light used for color mapping the OCT data can be aplurality of different wavelengths sent simultaneously or narrowband ofwavelengths or single wavelengths can be sent through the coresequentially and then collected by the cladding for processing andgenerating a color representation.

FIG. 17B illustrates another embodiment of an imaging fiber tip or probetip 175 for an OCT imaging probe configured for spectroscopic signalcollection. The imaging fiber 175 is disposed in a lumen 165 havingwalls 164. Light from a source (not shown) is focused to a point orregion 178 on the lumen wall 164. As shown, the fiber or prove tip 175is configured for side scanning such that it can image lumen objects 174or material disposed in the lumen 165 such as plaques 174. A lens suchas a grin lens or other optical element 172 is in optical communicationwith the imaging fiber tip 175. A beam director 176 is also use todirect the beam to the side such that the walls of the lumen 164 can beimaged. The fiber tip 175 includes a core 20, a cladding 24, and ajacket 27. In some embodiments, jacket 27 is absent. Typically, thefiber core 20 is in optical communication with the optical source, aninterferometer and one or more detectors such as photodiode-basedreceivers or detectors. The beam director or reflector 176 shown rotateswith the fiber 175 such that OCT and spectroscopy data can be collectedwith respect to the lumen walls 174 and related substructures.

As shown, by the light rays and arrows, light from the core 20 depictedas ray spanning an area of the lumen, is identified as a dotted pair oflines that propagate from the core 20 and into the lumen 165 untilreaching a focus 178 on lumen wall 164. After the light from the core 20is scattered from the lumen wall 174, it is received by the core 20 andcladding 24 as shown by the solid lines and arrows point to the cladding24. This light propagates along the imaging fiber portion 175 until itis coupled out of a fiber portion from a cladding layer and through theouter surface of the fiber portion for spectroscopic processing. Thisunguided light, which has been reflected back and forth along thecladding boundary, is used for color information and not imageformation. In contrast, the light traveling in the core continues untilreceived by a detector in electrical or optical communication with anOCT subsystem. Once received, this guided light is used to generateimages which can then be color indexed using the other signals from thecladding.

In the description, the invention is discussed in the context ofrotating imaging or forward scanning probes; however, these embodimentsare not intended to be limiting and those skilled in the art willappreciate that the invention can also be used for other types ofimaging applications, including non-biological applications.

The use of headings and sections in the application is not meant tolimit the invention; each section can apply to any aspect, embodiment,or feature of the invention.

Throughout the application, where compositions are described as having,including, or comprising specific components, or where processes aredescribed as having, including or comprising specific process steps, itis contemplated that compositions of the present teachings also consistessentially of, or consist of, the recited components, and that theprocesses of the present teachings also consist essentially of, orconsist of, the recited process steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components and can be selected from a groupconsisting of two or more of the recited elements or components.Further, it should be understood that elements and/or features of acomposition, an apparatus, or a method described herein can be combinedin a variety of ways without departing from the spirit and scope of thepresent teachings, whether explicit or implicit herein.

The use of the terms “include,” “includes,” “including,” “have,” “has,”or “having” should be generally understood as open-ended andnon-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa)unless specifically stated otherwise. Moreover, the singular forms “a,”“an,” and “the” include plural forms unless the context clearly dictatesotherwise. In addition, where the use of the term “about” is before aquantitative value, the present teachings also include the specificquantitative value itself, unless specifically stated otherwise. As usedherein, the term “about” refers to a ±10% variation from the nominalvalue.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present teachings remainoperable. Moreover, two or more steps or actions may be conductedsimultaneously.

Where a range or list of values is provided, each intervening valuebetween the upper and lower limits of that range or list of values isindividually contemplated and is encompassed within the invention as ifeach value were specifically enumerated herein. In addition, smallerranges between and including the upper and lower limits of a given rangeare contemplated and encompassed within the invention. The listing ofexemplary values or ranges is not a disclaimer of other values or rangesbetween and including the upper and lower limits of a given range.

The aspects, embodiments, features, and examples disclosed herein are tobe considered illustrative in all respects and are not intended to limitthe invention, the scope of which is defined only by the claims. Otherembodiments, modifications, and usages will be apparent to those skilledin the art without departing from the spirit and scope of the claimedinvention.

What is claimed is:
 1. A method of collecting optical coherence data andspectroscopic data from a sample comprising the steps of: transmittinglight in an optical fiber core having a first index of refraction to thesample; receiving light scattered from the sample; transmittingscattered light from the sample having a first mode in the optical fibercore to a first detector; transmitting scattered light from the samplehaving a second mode in a first cladding layer having a second index ofrefraction to a second detector; generating an optical coherencetomography image using the scattered light from the sample having thefirst mode; and overlaying spectroscopic data on the optical coherencetomography image, the spectrographic data obtained using the scatteredlight from the sample having the second mode.
 2. The method of claim 1wherein the scattered light having the first mode and the scatteredlight having the second mode are transmitted coaxially in the opticalfiber core and the first cladding layer, respectively.
 3. The method ofclaim 1 wherein the step of transmitting light in the optical fiber corehaving the first index of refraction to the sample further comprises thestep of rotating the optical fiber core.
 4. The method of claim 1wherein the scattered light having the second mode exits the firstcladding layer at an angle before reaching the second detector.
 5. Themethod of claim 1 wherein the optical coherence tomography image is a3-D image and the spectroscopy data is a color representation of thesample.
 6. The method of claim 1 further comprising the step ofcalibrating for collection efficiency such that the optical coherencetomography image is in focus.
 7. A method of collecting opticalcoherence data and spectroscopic data from a sample comprising:transmitting light along a first optical fiber core to the sample;receiving light scattered from the sample at a second optical fiber coreand an inner cladding, wherein the second optical fiber core and theinner cladding are concentrically arranged; transmitting scattered lightfrom the sample having a first mode from the first optical fiber core toa first detector, transmitting scattered light from the sample having asecond mode to a second detector; and generating an optical coherencetomography image of the sample having spectroscopic data overlaidthereon using the scattered light having the first mode and thescattered light having the second mode.
 8. The method of claim 7 whereinthe scattered light having the second mode exits the first claddinglayer at an angle before reaching the second detector.